"In Gum We Trust" spelled out in bubble gum in San Luis Obispo, California.
'In Gum We Trust' spelled out in chewed bubble gum in San Luis Obispo, California. (Photo: Peyri Herrera/Flickr)

It's no secret that chewing gum is an environmental nightmare.

Chewing gum is resilient, and it bonds extremely well to surfaces like concrete, asphalt and rubber. It's also non-water-soluble and typically not swallowed, so careless disposal of it can create an exceedingly expensive and laborious cleaning process.

That's why it's not uncommon to find dried-up blobs of chewing gum adhered to sidewalk pavement, the soles of shoes or the undersides of tables and chairs.

chewing gum on poleThat's also why an unintentional folk art phenomenon known as the "bubble gum wall" has such staying power.

These gunky walls might gross a lot of people out (because, yeah, they are pretty revolting), but you have to admit, they're impressive.

There are plenty of gum walls around the world (they often occur when people are idling in line at amusement parks, as seen at right), but none are quite as striking or as widely encompassing as the Market Theater Gum Wall in Seattle or the Bubble Gum Alley in San Luis Obispo, California.

Continue below to learn more about these dazzling yet disgusting tourist attractions.

Market Theater Gum Wall — Seattle, Washington

Windowsill dripping with bubble gum near Pike Place Market in Seattle.
(Photo: f11photo/Shutterstock)

Nestled underneath Seattle's famed Pike Place Market in Post Alley is the Market Theater Gum Wall, arguably one of the city's most fascinating (and germiest) tourist destinations.

Tourist stare in awe at the expansive Gum Wall in Seattle.
(Photo: f11photo/Shutterstock)

The origins of this offbeat locale date back to 1993 when bored theater patrons waiting to get into shows first began tacking gum and coins to the walls. There were multiple attempts by theater staff to remove the tacky build-up, but they eventually gave up when guests just kept adding more and more gum to the wall.

Flyers pinned up with gum on Seattle's Gum Wall
(Photo: N i c o l a/Flickr)

Within just a few years, the Gum Wall grew to immense proportions. Finally accepting its status as an offbeat yet culturally significant part of the city, it was officially recognized as a tourist attraction and landmark in 1999.

Pipes and brick wall covered in gum in Seattle
(Photo: Lane. V. Erickson/Shutterstock)

Many areas of the brick are covered in several inches of chewing gum, and some people even take it further by using the malleable substance to form words, phrases and symbols:

Word spelled out in gum at Seattle's Gum Wall
(Photo: TomKli/Shutterstock)

Despite the major ick factor, the Market Theater Gum Wall remains a novel delight to locals and tourist alike.

Seattle Gum Wall
(Photo: f11photo/Shutterstock)

Bubble Gum Alley — San Luis Obispo, California

Tourists visiting Bubble Gum Alley in San Luis Obispo, California.
(Photo: David Fulmer/Flickr)

No one knows for sure what led to the accumulation of used bubble gum on this 70-foot-long alley in downtown San Luis Obispo (some say it had to do with a school rivalry), but it's been cemented as a comically disgusting city tradition since at least the 1970s.

Detail of gum in Bubble Gum Alley.
(Photo: David Fulmer/Flickr)

Although Seattle had no major protests about incorporating the Market Theater Gum Wall into the fabric of city culture, the creation and maintenance of San Luis Obispo's Bubble Gum Alley was not so smooth. A consensus on appropriateness has yet to be reached, and while most locals agree that the odd spectacle is ultimately a boon for the city's downtown district, there are plenty others who still feel it's a tasteless and unsanitary eyesore.

Since the 1970s, there have been multiple attempts to remove the gum and clean up the alley after shop owners complained, but the sticky graffiti persists.

These days, locals understand that it's unlikely people will stop depositing their gum on the walls, which is why the only maintenance they attempt now is a deep steam clean once a month.

Tourists milling about Bubble Gum Alley
(Photo: David Fulmer/Flickr)

Of course, even though the vast majority of the city supports the alleyway and the valuable foot traffic it creates, it can still cause a few headaches, especially for the adjacent businesses, as pictured below:

Surrounding businesses must deal with stray bubble gum on their own buildings
(Photo: Peyri Herrera/Flickr)

Photo of bubble gum on pole: Edwin Verin/Shutterstock

Catie Leary ( @catieleary ) writes about science, travel, animals and the arts.